Conventionally, a motor vehicle is equipped with, e.g., an ECU (Engine Control Unit) in which a substrate is stored within an electronic device storage case. The electronic device storage case includes two members locked together by a male-female locking unit.
The male-female locking unit of the electronic device storage case includes a locking projection portion protruding from one of the members and a locking hole portion formed on the surface of the other member facing the surface of one member on which the locking projection portion exists. The locking projection portion is inserted into and locked with the locking hole portion.
In the electronic device storage case provided with the male-female locking unit, it is likely that a gap is left between the locking projection portion and the locking hole portion due to manufacturing errors or other causes. If the electronic device storage case having a gap between the locking projection portion and the locking hole portion is used in an ECU of a motor vehicle, the locking projection portion and the locking hole portion make repeated contact with each other due to the vibrations generated in the running motor vehicle. This poses a problem of abnormal noises such as buzz, squeak and rattle.
As a solution to this problem, there is known an electronic device storage case in which an elastic portion is provided in one of case members to elastically bias the case members away from each other when the case members are locked together by a locking projection portion and a locking hole portion (see, e.g., Japanese Application Publication No. 2003-37913).
The electronic device storage case provided with the elastic portion is configured such that, when the locking projection portion and the locking hole portion are brought into engagement with each other, the elastic portion provided in one of the case members presses the other case member away from one case member. In this manner, the locking projection portion and the locking hole portion are press-contacted against with each other through the elastic portion so that no gap can be generated between the locking projection portion and the locking hole portion. This helps suppress loose engagement of the locking projection portion and the locking hole portion, which assists in preventing generation of abnormal noises.
In the electronic device storage case disclosed in Japanese Application Publication No. 2003-37913, however, no consideration is given to those noises generated by a substrate within the storage case during occurrence of vibrations. In other words, the substrate may rattle within the storage case during occurrence of vibrations and may contact with the inner surface of the storage case, consequently generating abnormal noises.